Enamel composition, method for preparing enamel composition, and cooking appliance

ABSTRACT

An enamel composition, a method for preparing an enamel composition, and a cooking appliance are provided. The enamel composition may include phosphorus pentoxide (P2O5) at 15 to 50 wt %; silicon dioxide (SiO2) at 10 to 20 wt %; boron oxide (B2O3) at 1 to 15 wt %; one or more of lithium oxide (Li2O), sodium oxide (Na2O), or potassium oxide (K2O) at 5 to 20 wt %; one or more of sodium fluoride (NaF), calcium fluoride (CaF2), or aluminum fluoride (AlF3) at 1 to 5 wt %; one or more of magnesium oxide (MgO), barium oxide (BaO), or calcium oxide (CaO) at 1 to 35 wt %; and one or more of titanium dioxide (TiO2), cerium dioxide (CeO2), molybdenum trioxide (MoO3), bismuth oxide (Bi2O3), or copper oxide (CuO) at 10 to 25 wt %, such that a heating time required for cleaning may be shortened and oil contaminants may be completely removed.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Divisional application of U.S. patent applicationSer. No. 16/796,102, filed Feb. 20, 2020, which claims priority to andthe benefit of Korean Patent Application No. 10-2019-0021141, filed inKorea on Feb. 22, 2019, the disclosure of which is incorporated hereinby reference in its entirety.

BACKGROUND 1. Field

An enamel composition, a method for preparing an enamel composition, anda cooking appliance are disclosed herein.

2. Background

Enamel is a material made by applying a vitreous glaze onto a surface ofa metal plate. Common enamel is used in cooking appliances, such asmicrowaves and ovens. Cooking appliances, such as electric ovens and gasovens, for example, are appliances that cook food or other items(hereinafter, collectively “food”) using a heating source. Ascontaminants generated during cooking adhere to an inner wall of acavity of the cooking appliance, the inner wall of the cavity needs tobe cleaned. In this case, enamel applied onto the inner wall surface ofthe cavity of the cooking appliance facilitates removal of contaminantsadhered to the cooking appliance. Generally, a pyrolysis method, inwhich contaminants are burned at high temperature to produce ashes, isknown as a technique that easily cleans the inner wall of the cavity,and as a enamel composition to which the pyrolysis method can beapplied, an enamel composition containing components, such as phosphoruspentoxide (P₂O₅), silicon dioxide (SiO₂), and boron oxide (B₂O₃), forexample, is known.

However, the conventional enamel compositions consume a large amount ofenergy because the conventional enamel compositions enable cleaning onlywhen heated (pyrolyzed) under a condition of a high temperature of 450to 500° C. for about 4 hours. Further, in the case of the conventionalenamel compositions, oil contaminants, such as cattle, pig, and poultryoils, cannot be removed easily. Furthermore, enamel compositions shouldnot be denatured and damaged at a high temperature of 450 to 500° C.,but the conventional enamel compositions have a problem of degradationof durability at high temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the followingdrawings in which like reference numerals refer to like elements, andwherein:

FIG. 1 is a front perspective view of a cooking appliance according toan embodiment;

FIG. 2 is a partially enlarged cross-sectional view of an inner surfaceof a cavity of the cooking appliance of FIG. 1 ;

FIG. 3 is a partially enlarged cross-sectional view of an inner surfaceof a door of the cooking appliance of FIG. 1 ; and

FIG. 4 is a flow chart of method for preparing an enamel compositionaccording to an embodiment.

DETAILED DESCRIPTION

Enamel Composition

An enamel composition according to embodiments may include phosphoruspentoxide (P₂O₅) at 15 to 50 wt %; silicon dioxide (SiO₂) at 10 to 20 wt%; boron oxide (B₂O₃) at 1 to 15 wt %; one or more of lithium oxide(Li₂O), sodium oxide (Na₂O), or potassium oxide (K₂O) at 5 to 20 wt %;one or more of sodium fluoride (NaF), calcium fluoride (CaF₂), oraluminum fluoride (AlF₃) at 1 to 5 wt %; one or more of magnesium oxide(MgO), barium oxide (BaO), and calcium oxide (CaO) at 1 to 35 wt %; andone or more of titanium dioxide (TiO₂), cerium dioxide (CeO₂),molybdenum oxide (MoO₃), bismuth oxide (Bi₂O₃), or copper oxide (CuO) at10 to 25 wt %.

P₂O₅ is a component that functions to form an alkali phosphate glassstructure. In addition, P₂O₅ is a glass former that facilitates theaddition of a large amount of transition metal oxides to the enamelcomposition and helps water to penetrate between the enamel surface anda contaminant such that the contaminant is able to be easily removed.P₂O₅ may be included at 15 to 50 wt %. When P₂O₅ is included at greaterthan 50 wt %, vitrification of the enamel composition may be difficult,and thermal properties of the enamel composition may be degraded. WhenP₂O₅ is included at less than 15 wt %, an amount of added transitionmetal oxides may be decreased, degrading cleanability.

SiO₂ is a component that forms a glass structure. SiO₂ strengthens askeleton of the glass structure to enhance chemical resistance of theenamel composition. SiO₂ may be included at 10 to 20 wt %. When SiO₂ isincluded at greater than 20 wt %, it may interfere with the addition oftransition metal oxides, degrading cleanability. When SiO₂ is includedat less than 10 wt %, the glass composition may break down.

B₂O₃ serves as a glass former and is a component that acts to allow eachcomponent of the enamel composition to be uniformly melted. In addition,B₂O₃ serves to adjust a coefficient of thermal expansion and a fusionflow of the enamel composition to enhance coatability. B₂O₃ may beincluded at 1 to 15 wt %. When B₂O₃ is included at greater than 15 wt %,it may interfere with the addition of transition metal oxides to degradecleanability. When B₂O₃ is included at less than 1 wt %, the glasscomposition may break down, or the glass composition may becrystallized.

Li₂O, Na₂O, and K₂O serve to enhance cleanability of the enamelcomposition. One or more of Li₂O, Na₂O, or K₂O may be included at 5 to20 wt % in the enamel composition. When the one or more of the Li₂O, theNa₂O, or the K₂O are included at greater than 20 wt %, a coefficient ofthermal expansion of the glass may be greatly increased, degradingcoatability. When the one or more of the Li₂O, the Na₂O, or the K₂O areincluded at less than 5 wt %, cleanability may be degraded.

NaF, CaF₂, and AlF₃ are components that control a surface tension of anenamel coating layer to enhance surface characteristics of the enamelcoating layer. One or more of NaF, CaF₂, or AlF₃ may be included at 1 to5 wt % in the enamel composition. When the one or more of the NaF, theCaF₂, or the AlF₃ are included at greater than 5 wt %, thermalproperties may be degraded. When the one or more of the NaF, the CaF₂,pr AlF₃ are included at less than 1 wt %, surface characteristics of theenamel coating layer may be degraded.

MgO, BaO, and CaO are components that enhance adhesion between a enamelcoating layer and a base steel plate. One or more of MgO, BaO, or CaOmay be included at 1 to 35 wt % in the enamel composition. When the oneor more of the MgO, the BaO, or the CaO are included at greater than 35wt %, cleanability may be degraded. When the one or more of the MgO, theBaO, or the CaO are included at less than 1 wt %, adhesion between anenamel coating layer and a base steel plate may be decreased, degradingglass stability.

TiO₂, CeO₂, MoO₃, Bi₂O₃, and CuO function as catalysts on a surface ofan enamel coating layer. Therefore, TiO₂, CeO₂, MoO₃, Bi₂O₃, and CuOeasily cut attachment between the surface of an enamel coating layer anda contaminant. One or more of TiO₂, CeO₂, MoO₃, Bi₂O₃, or CuO may beincluded at 10 to 25 wt %. When the one or more of the above-listedcomponents are included at greater than 25 wt %, vitrification may bedifficult, and thermal properties may be degraded. On the other hand,when one or more of the above-listed components are included at lessthan 10 wt %, a catalytic reaction on the surface of an enamel coatinglayer may be reduced, degrading cleanability of enamel.

In addition, the enamel composition according to embodiments may furtherinclude aluminum oxide (Al₂O₃) at 1 to 20 wt %; zirconium dioxide (ZrO₂)at 1 to 5 wt %; and one or more of tin oxide (SnO) or zinc oxide (ZnO)at 1 to 10 wt %. Al₂O₃, ZrO₂, SnO, and ZnO compensate for low durabilityof an alkali phosphate glass structure and enhance hardness of theenamel surface. When Al₂O₃ is included at greater than 20 wt %, amelting temperature and fusion flow may be increased, degrading adhesionof an enamel coating layer. In addition, when ZrO₂ is included atgreater than 5 wt % or SnO and/or ZnO are/is included at greater than 10wt %, a glass structure may not be formed. When each component isincluded below its lower limit, durability of an enamel coating layermay be degraded.

Additionally, the enamel composition according to embodiments mayinclude the MoO₃ at 1 to 10 wt % and the CuO at 1 to 5 wt % to maximizecleanability and prevent durability of an enamel coating layer frombeing degraded. In a case of a phosphate-based enamel composition,especially when both Mo and Cu are included, cleanability is maximized.When MoO₃ is included at greater than 10 wt % and CuO is included atgreater than 5 wt %, an addition amount of other components isdecreased, and thus, vitrification of enamel may be difficult, anddurability may be degraded. On the other hand, when MoO₃ is included atless than 1 wt % and CuO is included at less than 1 wt %, cleanabilityof enamel may be degraded.

In addition, when the enamel composition according to embodimentsincludes both MoO₃ and Bi₂O₃, any one of the MoO₃ or the Bi₂O₃ may beincluded at 2 wt % or less. Mo and Bi may collide with each other in thephosphate-based enamel composition, and accordingly, metallic crystalsmay be precipitated on an enamel coating layer. Therefore, when both Moand Bi are included in the enamel composition according to embodiments,any one of the two components may be included at 2 wt % or less.

As mentioned above, the conventional enamel compositions consume a largeamount of energy because the conventional enamel compositions enablecleaning only when heated (pyrolyzed) under a condition of a hightemperature of 450 to 500° C. for about 4 hours. However, the enamelcomposition according to embodiments enables removal of sugarcontaminants containing sugar even when heated (pyrolyzed) under acondition of a high temperature of 450 to 500° C. for less than an hourdue to having the above-described novel composition ratio. Accordingly,use of the enamel composition according to embodiments provides aneffect of energy saving and a reduction in cleaning time. In addition,the enamel composition according to embodiments exhibits a superior oilcontaminant cleaning ability. Accordingly, hygiene of a cookingappliance using the enamel composition according to embodiments may beis easily managed.

Method for Preparing Enamel Composition

A method 100 of preparing an enamel composition according to embodimentsmay include providing the above-described enamel composition materials(120); melting the enamel composition materials (120); and quenching themelted enamel composition materials (130) to form an enamel composition.The materials may be sufficiently blended and then melted. The materialsmay be melted at 1,200 to 1,400° C. In addition, the materials may bemelted for 1 to 2 hours. Afterward, the melted materials may be quenchedby a quenching roller using a chiller, for example. As a result, theenamel composition may be formed.

Cooking Appliance

The enamel composition according to embodiments may be applied on onesurface of a target object to be coated with the enamel composition. Thetarget object may be a metal plate, a glass plate, or a portion orentirety of a cooking appliance. The enamel composition may be appliedonto an inner surface of the cavity of the cooking appliance or an innersurface of the door of the cooking appliance.

Referring to FIG. 1 , a cooking appliance 1 according to embodiments mayinclude a cavity 11 that forms a cooking chamber, a door 14 thatselectively opens and closes the cooking chamber, one or more heatingsources 13, 15, and 16 that provide heat to the cooking chamber, and acoating layer that is formed of the enamel composition according toembodiments applied onto an inner surface of the cavity 11 or an innersurface of the door 14.

The cavity 11 may be formed in a hexahedral shape, a front surface ofwhich is open. The heating sources 13, 15, and 16 may include aconvection assembly 13 that discharges heated air into the cavity 11, anupper heater 15 disposed at a top of the cavity 11, and a lower heater16 disposed at the bottom of a cavity 11. The upper heater 15 and thelower heater 16 may be provided inside or outside of the cavity 11. Ofcourse, the heating sources 13, 15, and 16 do not necessarily includethe convection assembly 13, the upper heater 15, and the lower heater16. That is, the heating sources 13, 15, and 16 may include one or moreof the convection assembly 13, the upper heater 15, or the lower heater16.

Referring to FIG. 3 and FIG. 4 , the enamel composition according toembodiments may be applied onto an inner surface of the cavity 11 of thecooking appliance 1 or an inner surface of the door 14 thereof by a dryprocess or a wet process. The cavity 11 and the door 14 may be formed ofa metal plate, and coating layers 17 and 18 formed of the enamelcomposition according to embodiments may be directly formed as a singlelayer on the metal plate.

According to the dry process, the enamel composition materials may bedispersed in an organic binder, and the enamel composition materials andorganic binder, which have been blended, may be subjected to milling ina ball mill to prepare frit. On the other hand, according to the wetprocess, the enamel composition materials may be dispersed in water(H₂O) and a pigment, and the enamel composition materials, water (H₂O),and pigment, which have been blended, may be subjected to milling in aball mill to prepare frit.

Afterward, the frit prepared by the dry process or the wet process maybe applied onto an inner surface of the cavity 11 of the cookingappliance 1 or an inner surface of the door 14 thereof by a sprayingmethod. The applied frit may be fired at 600 to 900° C. for 100 to 450seconds and applied on an inner surface of the cavity 11 of the cookingappliance 1 or an inner surface of the door 14 thereof.

Hereinafter, embodiments will be described with respect to examples.

Examples

Preparation of Enamel Composition

Enamel compositions were prepared in the compositions shown in Table 1below. Raw materials of components were sufficiently blended in aV-mixer for 3 hours. In this case, ammonium dihydrogen phosphate(NH₄H₂PO₄) was used as a raw material of phosphorus pentoxide (P₂O₅),and sodium carbonate (Na₂CO₃), potassium carbonate (K₂CO₃), and lithiumcarbonate (Li₂CO₃) were used, respectively, as raw materials of Na₂O,K₂O, and Li₂O. The blended material was sufficiently melted at 1,300° C.for one and a half hours and then quenched in a quenching roller toobtain cullet.

An initial particle size of the cullet thus obtained by the aboveprocess was controlled using a grinder (ball mill), and then, theresulting cullet was ground using a jet mill for about 5 hours andpassed through a 325 mesh sieve (ASTM C285-88) to control the particlediameter thereof to be 45 μm or less, thereby preparing frit (a powder).

TABLE 1 Comparative Components Examples Examples (wt %) 1 2 3 4 1 2 SiO₂13.82 14.97 13.49 14.16 0 42.7 P₂O₅ 21.2 20.2 22.98 24.13 45.31 0 B₂O₃11.66 9.41 9.73 10.22 0 0 Na₂O 4 4.79 4.06 4.27 1.95 1.95 K₂O 9.94 10.7611.24 11.8 4.79 4.79 Li₂O 0.84 0.91 0 0 0 0 NaF 1.67 1.81 1.55 1.62 0 0MgO 0 0 0 0 7.59 10.2 Al₂O₃ 15.9 17.21 14.82 15.56 0 0 CaO 0 0 0 0 2.92.9 TiO₂ 0.85 0.92 18.55 1.33 1.95 1.95 CuO 3.39 0 0 10 0 0 ZnO 5.09 0 00 0.97 0.97 ZrO₂ 2.31 4.34 2.31 2.43 0 0 MoO₃ 9.33 1.84 1.27 4.48 9.899.89 SnO 0 0.92 0 0 0 0 BaO 0 0 0 0 19.71 19.71 Bi₂O₃ 0 9.17 0 0 4.944.94 CeO₂ 0 2.75 0 0 0 0

Manufacture of Enamel Composition Specimen

Each of the frits prepared using the enamel compositions according toExamples 1 to 5 and Comparative Examples 1 and 2 was sprayed on a lowcarbon steel sheet having an area of 200 (mm)×200 (mm) and a thicknessof 1 (mm) or less using a corona discharge gun. In this case, a voltageof the discharge gun was controlled under a condition within the rangeof 40 kV to 100 kV, and an amount of the frit sprayed on the low carbonsteel sheet was 300 g/m 2. The low carbon steel on which the frit hadbeen sprayed was fired at 830° C. to 870° C. for 300 to 450 seconds toform a coating layer on one surface of the low carbon steel. In thiscase, the coating layer was formed to have a thickness of about 80 μm to250 μm. As a result, specimens according to Examples 1 to 7 andComparative Examples 1 to 3 were manufactured.

Experimental Example

The specimens according to Examples and Comparative Examples wereevaluated for abilities as described below, and results thereof areshown in Table 4.

1. Cleanability Against Chicken Oil Contaminant

1 g of chicken oil as a contaminant was uniformly and thinly spread on asurface of the specimen, in which a metal substrate (100 (mm)×100 (mm))had been coated with the enamel composition, with a brush, and thespecimen to which the contaminant had been applied was placed in athermostat at 250 to 290° C. for an hour to solidify the contaminant.After solidification of the contaminant, the resulting specimen wascooled naturally, and the contaminant was burned at 400° C. for an hour.Afterward, the hardened contaminant was subjected to back and forth (oneround trip) wiping at a force of 3 kgf or less with a scouring pad for afrying pan which had been soaked with room-temperature water. A portionwiped on the contaminated specimen surface was uniformalized using astick whose bottom has a diameter of 5 cm and is flat.

2. Cleanability Against Monster Mash

In addition, cleanability against monster mash was measured by the samemethod as described above. In this case, a number of round trips ofwiping the specimen was measured and defined as the number of roundtrips for cleaning, and evaluation standards for cleanability are shownin Table 2.

TABLE 2 Number of round trips for cleaning Level  1~5 LV.5  6~15 LV.416~25 LV.3 26~50 LV.2 51~ LV.1

3. Evaluation of Durability

The specimens which had undergone the cleaning test according to theabove item 2 were evaluated for durability, such as heat resistance andchemical resistance. The durability of each specimen was evaluated bydetermining a staining phenomenon. The staining phenomenon wasdetermined by observing the surface of each specimen and quantifying aratio of the area of the residue or stain to the entire surface area.Evaluation standards for the staining phenomenon are the same as shownin Table 3.

TABLE 3 Stained area ratio Level    0% LV.5 ~20% LV.4 ~50% LV.3 ~80%LV.2     80%~ LV.1

TABLE 4 Comparative Examples Examples 1 2 3 4 1 2 Cleanability LV.5 LV.5LV.5 LV.5 LV.2 LV.2 against chicken oil Cleanability LV.5 LV.5 LV.5 LV.5LV.2 LV.1 against monster mash Stain level LV.5 LV.5 LV.5 LV.5 LV.2 LV.1

As shown in Table 4, it can be seen that Examples according toembodiments exhibited not only excellent cleanability but also excellentdurability. On the other hand, it can be seen that Comparative Examplesexhibited not only degraded cleanability due to not having an optimalcomposition ratio but also highly unsatisfactory durability due to anunstable glass composition, as compared with Examples according toembodiments.

The enamel composition according to according to embodiments maydramatically reduce a heating time in comparison to a conventionalenamel composition. Accordingly, the enamel composition according toembodiments may save energy consumed in cleaning due to the shortenedheating time.

Further, the enamel composition according to embodiments may allowespecially oil contaminants to be completely removed. Accordingly, theenamel composition according to embodiments may enhance hygiene of acooking appliance

Furthermore, the enamel composition according to embodiments may exhibitenhanced adhesion to a base steel plate and also ensure excellentcleanability due to a special component ratio. Also, as the enamelcomposition according to embodiments may include a phosphate-basedcomponent in an optimal composition ratio, it can exhibit high heatresistance and high chemical durability as well as excellentcleanability. Additionally, as the enamel composition according toembodiments may be directly applied as a single layer onto a base steelplate in the absence of an intermediate buffer layer, the layer may besimply formed.

Embodiments disclosed herein provide a novel enamel composition whichallows a heating time required for cleaning to be shortened. Embodimentsdisclosed herein provide a novel enamel composition which allows oilcontaminants to be completely removed. Further, embodiments disclosedherein provide a novel enamel composition which is excellent in not onlycleanability but also durability, such as heat resistance and chemicalresistance.

In order to provide an enamel composition which enables cleaning whileshortening a heating time in comparison to a conventional enamelcomposition, a enamel composition according to embodiments may includeP₂O₅ at 15 to 50 wt %; SiO₂ at 10 to wt %; B₂O₃ at 1 to 15 wt %; one ormore of Li₂O, Na₂O, or K₂O at 5 to 20 wt %; one or more of NaF, CaF₂, orAlF₃ at 1 to 5 wt %; one or more of MgO, BaO, or CaO at 1 to 35 wt %;and one or more of TiO₂, CeO₂, MoO₃, Bi₂O₃, or CuO at 10 to 25 wt %. Inaddition, in order to provide a phosphate-based enamel composition whichenables removal of oil contaminants, that is, which exhibits maximizedcleanability, an enamel composition according to embodiments mayinclude, when both the MoO₃ and the Bi₂O₃ are included, any one of theMoO₃ or the Bi₂O₃ at 2 wt % or less.

Additionally, in order to provide a novel enamel composition whichexhibits high heat resistance and high chemical durability as well asexcellent cleanability, an enamel composition according to embodimentsmay further include Al₂O₃ at 1 to 20 wt %; ZrO₂ at 1 to 5 wt %; and oneor more of SnO or ZnO at 1 to 10 wt % and may include the MoO₃ at 1 to10 wt % and the CuO at 1 to 5 wt %.

Although embodiments have been described above with reference to theillustrated drawings, it is obvious that embodiments are not limited tothe embodiments and drawings disclosed herein, and various modificationsmay be made by those skilled in the art within the spirit and scope. Inaddition, even when the effect of the configuration is not explicitlydescribed while the above-described embodiments are described, it isobvious that the effect predictable by the corresponding configurationshould also be recognized.

It will be understood that when an element or layer is referred to asbeing “on” another element or layer, the element or layer can bedirectly on another element or layer or intervening elements or layers.In contrast, when an element is referred to as being “directly on”another element or layer, there are no intervening elements or layerspresent. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third,etc., may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section could be termed a second element,component, region, layer or section without departing from the teachingsof the present invention.

Spatially relative terms, such as “lower”, “upper” and the like, may beused herein for ease of description to describe the relationship of oneelement or feature to another element(s) or feature(s) as illustrated inthe figures. It will be understood that the spatially relative terms areintended to encompass different orientations of the device in use oroperation, in addition to the orientation depicted in the figures. Forexample, if the device in the figures is turned over, elements describedas “lower” relative to other elements or features would then be oriented“upper” relative to the other elements or features. Thus, the exemplaryterm “lower” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (rotated 90 degrees or at otherorientations) and the spatially relative descriptors used hereininterpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Embodiments are described herein with reference to cross-sectionillustrations that are schematic illustrations of idealized embodiments(and intermediate structures). As such, variations from the shapes ofthe illustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, embodiments should not beconstrued as limited to the particular shapes of regions illustratedherein but are to include deviations in shapes that result, for example,from manufacturing.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment. The appearances ofsuch phrases in various places in the specification are not necessarilyall referring to the same embodiment. Further, when a particularfeature, structure, or characteristic is described in connection withany embodiment, it is submitted that it is within the purview of oneskilled in the art to effect such feature, structure, or characteristicin connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. An enamel composition, comprising: phosphorus pentoxide (P₂O₅) at 15 to 50 wt %; silicon dioxide (SiO₂) at 10 to 20 wt %; boron oxide (B₂O₃) at 1 to 15 wt %; one or more of lithium superoxide (Li₂O), sodium oxide (Na₂O), or potassium oxide (K₂O) at 5 to 20 wt %; one or more of sodium fluoride (NaF), calcium fluoride (CaF₂), or aluminum fluoride (AlF₃) at 1 to 5 wt %; one or more of magnesium oxide (MgO), barium oxide (BaO), or calcium oxide (CaO) at 1 to 35 wt %; and one or more of titanium dioxide (TiO₂), cerium dioxide (CeO₂), molybdenum trioxide (MoO₃), bismuth oxide (Bi₂O₃), or copper oxide (CuO) at 10 to 25 wt %, wherein when both the MoO₃ and the Bi₂O₃ are included, any one of the MoO₃ or the Bi₂O₃ is included at 2 wt % or less.
 2. The enamel composition of claim 1, further comprising: aluminum oxide (Al₂O₃) at 1 to 20 wt %; zirconium dioxide (ZrO₂) at 1 to 5 wt %; and one or more of tin oxide (SnO) or zinc oxide (ZnO) at 1 to 10 wt %. 